Fatal Error - please help (2 posts)

I tried to upload suffusion 3.5.0 theme from my server to wordpress.org after doing this I went to my blog and there is this message on the page
Fatal error: Call to undefined function post_class() in /home/dew008/public_html/wp-content/themes/suffusion/layouts/layout-blog.php on line 20
I don't know what to do to fix it.